Spring架构中涉及了很多设计模式,本文来介绍下Spring中在AOP实现时Adapter模式的使用。AOP本质上是Java动态代理模式的实现和适配器模式的使用,关于这两种设计模式的具体介绍烦请参考我之前的文章
Java代理模式
Java适配器模式(adapter)
文章目录
Spring中适配器模式
一、AOP案例
1.相关依赖
2.创建目标对象
3.创建通知
4.配置文件
5.测试
二、适配器应用解析
1.Advice体系结构
2.适配器的实现
2.1Adaptee
2.2target
2.3Adapter
2.4Client
Spring中适配器模式
一、AOP案例
Spring中的AOP的实现方式有多种,而且每种实现方式中的通知类型也比较多,本文以Spring自带的Schema-base方式中的前置通知来说明。详细介绍移步 Spring之AOP详解
1.相关依赖
<dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> <version>4.3.21.RELEASE</version> </dependency> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.12</version> </dependency> <dependency> <groupId>aopalliance</groupId> <artifactId>aopalliance</artifactId> <version>1.0</version> </dependency>
2.创建目标对象
/** * 目标对象 接口 * @author 波波烤鸭 * @email dengpbs@163.com * */ public interface SomeService { public void doSome(); }
/** * 目标对象 * @author 波波烤鸭 * @email dengpbs@163.com * */ public class SomeServiceImpl implements SomeService { @Override public void doSome() { System.out.println("目标对象....方法执行了"); } }
3.创建通知
/** * 前置通知 * 需要实现MethodBeforeAdvice接口 * @author 波波烤鸭 * @email dengpbs@163.com * */ public class MyMethodBeforeAdvice implements MethodBeforeAdvice { /** * method 目标方法 * args 目标方法参数列表 * target 目标对象 */ @Override public void before(Method method, Object[] args, Object target) throws Throwable { System.out.println("前置通知执行了...."); } }
4.配置文件
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.3.xsd"> <!-- 注册目标类 --> <bean id="someServiceImpl" class="com.dpb.service.SomeServiceImpl" ></bean> <!-- 注册前置通知 --> <bean class="com.dpb.schema.MyMethodBeforeAdvice" id="myMethodBeforeAdvice"></bean> <!-- 注册代理类 --> <bean id="proxyFactoryBean" class="org.springframework.aop.framework.ProxyFactoryBean"> <!-- 指定目标对象 --> <property name="target" ref="someServiceImpl"/> <!-- 指定目标类实现的所有接口 --> <property name="interfaces" value="com.dpb.service.SomeService"/> <!-- 指定切面 --> <property name="interceptorNames" > <list> <value>myMethodBeforeAdvice</value> </list> </property> </bean> </beans>
5.测试
@Test public void test1() { ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml"); // 注意通过getBean获取增强的代理类!!! SomeService some = ac.getBean("proxyFactoryBean",SomeService.class); some.doSome(); }
输出:
说明我们配置的前置通知生效了,在目标方法执行之前执行了。
二、适配器应用解析
1.Advice体系结构
说明:
advice的类型有:BeforeAdvice,AfterReturningAdvice,ThrowsAdvice等
每个类型的通知都有对应的拦截器
advice 拦截器
BeforeAdvice MethodBeforeAdviceInterceptor
AfterAdvice AfterReturningAdviceInterceptor
AfterAdvice ThrowsAdviceInterceptor
Spring容器需要将每个具体的advice封装成对应的拦截器,返回给容器,这里对advice转换就需要用到适配器模式。
2.适配器的实现
以前置通知为例
2.1Adaptee
public interface MethodBeforeAdvice extends BeforeAdvice { void before(Method method, Object[] args, Object target) throws Throwable; }
2.2target
Adapter的接口 AdvisorAdapter
public interface AdvisorAdapter { // 判断通知类型是否匹配 boolean supportsAdvice(Advice advice); // 获取对应的拦截器 MethodInterceptor getInterceptor(Advisor advisor); }
2.3Adapter
MethodBeforeAdviceAdapter
class MethodBeforeAdviceAdapter implements AdvisorAdapter, Serializable { @Override public boolean supportsAdvice(Advice advice) { return (advice instanceof MethodBeforeAdvice); } @Override public MethodInterceptor getInterceptor(Advisor advisor) { MethodBeforeAdvice advice = (MethodBeforeAdvice) advisor.getAdvice(); // 通知类型匹配对应的拦截器 return new MethodBeforeAdviceInterceptor(advice); } }
2.4Client
代理类通过DefaultAdvisorAdapterRegistry类来注册相应的适配器。
public class DefaultAdvisorAdapterRegistry implements AdvisorAdapterRegistry, Serializable { private final List<AdvisorAdapter> adapters = new ArrayList<AdvisorAdapter>(3); /** * Create a new DefaultAdvisorAdapterRegistry, registering well-known adapters. */ public DefaultAdvisorAdapterRegistry() { // 注册相应的适配器 registerAdvisorAdapter(new MethodBeforeAdviceAdapter()); registerAdvisorAdapter(new AfterReturningAdviceAdapter()); registerAdvisorAdapter(new ThrowsAdviceAdapter()); } // 包装类 将通知转换为了 对应的适配器 // 本案例中将 MyMethodBeforeAdvice转换为了MethodBeforeAdviceAdapter @Override public Advisor wrap(Object adviceObject) throws UnknownAdviceTypeException { if (adviceObject instanceof Advisor) { return (Advisor) adviceObject; } if (!(adviceObject instanceof Advice)) { throw new UnknownAdviceTypeException(adviceObject); } Advice advice = (Advice) adviceObject; if (advice instanceof MethodInterceptor) { // So well-known it doesn't even need an adapter. return new DefaultPointcutAdvisor(advice); } for (AdvisorAdapter adapter : this.adapters) { // Check that it is supported. if (adapter.supportsAdvice(advice)) { return new DefaultPointcutAdvisor(advice); } } throw new UnknownAdviceTypeException(advice); } // 获取适配器对应的所有的拦截器 @Override public MethodInterceptor[] getInterceptors(Advisor advisor) throws UnknownAdviceTypeException { List<MethodInterceptor> interceptors = new ArrayList<MethodInterceptor>(3); Advice advice = advisor.getAdvice(); if (advice instanceof MethodInterceptor) { interceptors.add((MethodInterceptor) advice); } for (AdvisorAdapter adapter : this.adapters) { if (adapter.supportsAdvice(advice)) { // 调用了适配器的方法 interceptors.add(adapter.getInterceptor(advisor)); } } if (interceptors.isEmpty()) { throw new UnknownAdviceTypeException(advisor.getAdvice()); } return interceptors.toArray(new MethodInterceptor[interceptors.size()]); } @Override public void registerAdvisorAdapter(AdvisorAdapter adapter) { this.adapters.add(adapter); } }
本案例中的适配器中的方法是
@Override public Object invoke(MethodInvocation mi) throws Throwable { // 前置通知方法 this.advice.before(mi.getMethod(), mi.getArguments(), mi.getThis()); // 目标对象的方法 return mi.proceed(); }
~ 好了 AOP中的适配器的分析就到此了。关于AOP中的代理的实现抽空再来分析